Server not able to connect client

[Kapil Gupta]

Hi All,

I have a C++ application which runs a server on some specific port (say 5001).I have also a java client which will connect to this server and can do some predefine tasks.

In windows XP,
I am able to run java client which do
Runtime.getRuntime().exec(cmd); // my c++ application
and create sockect and is connected to the server.like

do {
scomm = new Socket("Computer-Name", port);
} while (!scomm.isConnected());

everything works fine in windows XP.

But the same thing fails in 64 bit operating system Vista, Intel(R) Core(TM) 2 CPU.
Throwing error java.net.ConnectException.
Stack trace doenot yield much info.

java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(UnKnown Source)
at java.net.PlainSocketImpl.connectToAddress(UnKnown Source)
at java.net.PlainSocketImpl.connect(UnKnown Source)
at java.net.SocksSocketImpl.connect(UnKnown Source)
at java.net.Socket.connect(UnKnown Source)
at java.net.Socket.connect(UnKnown Source)
at java.net.Socket.<init>(UnKnown Source)
at java.net.Socket.<init>(UnKnown Source)


If I ran server on vista and the client ( this time I am not calling exec) on XP or vice versa, socket is able to establish connection.
So the problem lies only when both client and server runs on Vista. Can somebody plz help ?

Thanks in anticipation
Kapil

[Kapil Gupta]

No replies :(

[Eranga]

Normally connection refused found when the port is not listen. Did you check that your post can listen on Vista.

[Kapil Gupta]

Hi Eranga,

I have tried with different ports also. One point to notice here is :

If I ran server on vista and the client ( this time I am not calling exec) on XP or vice versa, socket is able to establish connection. So the problem lies only when both client and server runs on Vista.

Is this Operating system issue? or security issue or bad code written ?

Thanks
Kapil

[Eranga]

Is this Operating system issue? or security issue or bad code written ?

Hopefully I think this is an issue with the code. But I don't know to say anything about system issues. Because on Vista I didn't get any such issues.

[Kapil Gupta]

Hi,

I think this issue is something related to Vista 64bit security. As the same code is working fine in 64 bit Win XP machine, 32 bit Vista machine and 32 bit XP machine.

Regards,
Kapil

[Eranga]

How can you exactly it's security issue. Still there can be some bad coding, which have conflict with 64bits.

[Kapil Gupta]

Hi Eranga,

I think you are right, I noticed that if I ran my jar file from command prompt with command:

java -jar -cp . Filename.jar


Socket is able to connect to server. But if I double click on the jar file, it is not able to connect.

I am spawning a new process to create server by

p = Runtime.getRuntime().exec(cmd,null,new File(execPath));

and connecting to it by

try {
InetAddress address = InetAddress.getLocalHost();
do {
scomm = new Socket(address, port);
} while (!scomm.isConnected());
} catch ......

Is this problem specific to jar file ?

Waiting for reply,
Kapil

[Eranga]

I don't think this is specific to jar file. Did you get any warning/error message when you double click on the jar file, I guess you have. Basically it can be conflict with class path.

[leaf]

In the java socket programming, is it possible to identify that the current connect is establised by a telnet session and not through an application.

Socket s = m_sock.accept();

SK

[california_kiwi]

I'm seeing similar odd behavior.

I have a simple server built in visual basic, listening to port 5555. In VB, it's
Dim Listener As New UdpClient(5555).

I have simple client built in Java to communicate to the server. It cannot seem to communicate to the server on my local machine. I'm receiving an IO Exception. This is java code that I've used successfully on Win 2000 OS.

If I point the client to any other IP address that is not on my machine, it is fine.

What's odd, is that I've also used a simple VB client, which was able to communicate to the server on my local machine locally successfully.

While I won't rule out a programming issue, I'm suspecting something else. I'm highly suspicious that it's some sort of security setup. I've turned off the firewall and security, but that did not fix anything.

I've tried having the client communicate to the server on localhost as well as 127.0.0.1, and it doesn't work. It behaves as if it can't see the local machine.

In my searches, I stumbled on a site discussing 'netsh interface tcp set global autotuning=disabled', but I was unable to run it on my machine; I received a response "Set global command failed on IPv4 The requested operation requires elevation."

netstat -a reveal the port listening at 0.0.0.0:5555.

Any thoughts or comments?

[Eranga]

At the time of your client directing to your PC, that socket is listening through the specified port?

[california_kiwi]

yes. Both server and client are set to the same port, in this case 5555. I've done additional searches today and have found several instances of folks having client/server apps in java unable to communicate on the same machine utilizing Vista. Unfortunately, all were left unanswered.

I continue to suspect it's some sort of Vista security item. I attempted to make adjustments to firewall settings, but had no success.

Any insight would be appreciated.

[Eranga]

Can't you test with port 5001. Because using that you can avoid all firewall and stuff.

By the way, what are instance that you found effect to communicate in vista.

[california_kiwi]

Alright, I figured out the problem. The issue had nothing to do with firewalls or Windows Vista.

My problem was a fundamental network miscommunication. The server I had was listening for a UDP packet. The client was sending TCP.

I wrote a UDP client and problem solved!

Once I figured that out, I got things where I wanted them to be, which was a TCP client/server.

Thanks for the assistance!

CK

[Eranga]

Nice, if you solve the problem, it's better to make the thread solved. :)